Field of the Invention
The invention relates to an impeller and a fan and, more particularly, to an impeller whose centrifugal blades are arranged periodically and a fan using the same.
Description of the Related Art
Electronic devices generate heat while operating, and if the heat is not dissipated efficiently, the electronic devices may easily crash, or electronic elements of the electronic device may be damaged, which results in property loss and may hurt the user. Therefore, a fan is usually disposed in the electronic device to solve the overheating problem. The fan blows wind to bring the heat generated, by the electronic device away via forced convection.
Since performance of an electronic chip is improved with more heat generated, the temperature in the electronic device grows higher, and thus the rotating speed of a motor in the fan increases continually. Though air velocity of the fan can be increased by improving the rotating speed of the motor, the fan with the high rotating, speed generates more noise, which annoys users.
The conventional fan includes an impeller and a casing. The impeller includes a plurality of blades, and the casing includes a tongue for increasing pressure. When the blades of the impeller pass the tongue, airflow noise in a constant frequency is generated due to the length of each of the blades being the same and a distance between each blades and the tongue being constant. Continuous noise in a constant frequency can accumulate and generate noise peak, which discomforts the user.